writerfilter: drop support for simple list types without constants

In other words, from now it's a must to map ST_Foo simple types to
NS_ooxml::LN_something constants, and raw integers (which are hard to
grep and hard to track down where are they used) are no longer an
option.

Change-Id: I968b27bca3f64f6f4a382b87e2dbc499a3132ea2

writerfilter/source/ooxml/factoryimpl_ns.py

@@ -200,11 +200,8 @@ def factoryAttributeToResourceMap(nsNode):
 
 
 def idToLabel(idName):
-    if ":" in idName:
-        ns, ln = idName.split(':')
-        return "NS_%s::LN_%s" % (ns, ln)
-    else:
-        return idName
+    ns, ln = idName.split(':')
+    return "NS_%s::LN_%s" % (ns, ln)
 
 
 def appendValueData(values, name, value):